System and method for applying augmentation corrections for GNSS positioning

ABSTRACT

A method for determining a position using a GNSS system having a plurality of GNSS satellites and one or more augmentation systems, which method includes the steps of obtaining a code or phase measurement from the GNSS satellite signals, generating measurement groups, and generating corrected measurement groups by applying code or phase corrections from the augmentation systems, and applying combinations of the corrected measurements in a filter which outputs a position and ambiguity estimate.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the priority benefit of U.S. Provisional PatentApplication No. 61/264,555 filed on Nov. 25, 2009 entitled “System andMethod for Applying Augmentation Corrections for GNSS Positioning, thecontents of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to positioning using a Global NavigationSatellite System and more particularly to correcting errors for code andphase measurements from a Global Navigation Satellite System to achievea positioning result.

BACKGROUND

Global Navigation Satellite System (GNSS) is the commonly accepted termfor positioning systems based on line of sight radio from orbitingsatellites. GNSS positioning applies the simultaneous range to a minimumof four GNSS satellites from a receiver, along with the known satellitecoordinates obtained from the broadcasted navigation messages, todetermine the three dimensional coordinates of the receiver position anda receiver clock offset. Existing GNSSs include the Global PositioningSystem (GPS) funded and controlled by the U.S. Department of Defense,the GLObal NAvigation Satellite System (GLONASS) founded and controlledby Russia, the GALILEO system founded and controlled by Europe, theBeidou system founded and controlled by China and the Quasi-ZenithSatellite System (QZSS) founded and controlled by Japan.

For a typical GNSS system, the navigation satellites transmit two typesof measurements; the code portion allowing a code pseudorangemeasurement to be determined and the carrier portion allowing a carrierphase measurement to be determined. The code pseudorange is anunambiguous measurement of distance to the satellite transmitting thesignal, but with relatively poor measurement accuracy. The carrier phasemeasurement has better measurement accuracy, but always contains anambiguity due to the unknown number of carrier wavelengths existing inthe phase measurement.

However, since the signals being transmitted between the satellites andthe receiver are subjected to numerous errors, such as satellite orbitand clock errors, atmospheric delay, environmental effects and the like,position determined even using the carrier portion is not completelyaccurate. Augmentation systems, which determine errors and providecorrections to code pseudorange measurements and carrier phasemeasurements, have been developed to mitigate these errors. Theaugmentation systems can be ground based or satellite based and somefreely provide the corrections whereas others require a subscription inorder to use the corrections. These augmentation systems include codepseudorange based augmentation systems such as the Wide AreaAugmentation System (WAAS) covering North America, the EuropeanGeostationary Navigation Overlay System (EGNOS) covering Europe, theMultifunctional Transport Satellite Space bases Augmentation System(MSAS) covering East Asia, GPS Aided Geo Augmented Navigation (GAGAN)covering India, and local DGPS systems to provide code pseudorangecorrections and carrier phase based systems, such as OmniStar™,StarFire™ and CORS systems to provide carrier phase measurementcorrections.

A typical existing GNSS receiver can apply code corrections or phasecorrections from publicly available systems or privately owned systems.Code corrections generally offer less of an accuracy improvement ascompared to phase corrections. However, phase correction based systemshave a relatively longer initialization period, typically 20 to (30minutes. There is a need in the art for methods and systems to optimallycombine these two kinds of corrections in one receiver to achieve apositioning result that has the fast initialization of code correctionsand the higher accuracy of phase corrections.

SUMMARY OF THE INVENTION

In one aspect, the invention may comprise a method for determining aposition using a GNSS systems having a plurality of GNSS satellites andone or more augmentation systems, the method comprising the step ofreceiving signals transmitted by the GNSS satellites, and furthercomprising the sequential or non-sequential steps of:

a) obtaining a direct code or a direct phase measurement, or both, fromthe GNSS satellite signals;

b) generating a code measurement group by creating at least onecode-based additional measurement;

c) generating a phase measurement group by creating at least onephase-based additional measurement;

d) generating an IFCP measurement group by creating at least one IFCPmeasurement;

e) receiving at least one code correction from a code based augmentationsystem, or at least one phase correction from a phase based augmentationsystem, or both;

f) correcting one or more:

-   -   a. at least one measurement from the code measurement group with        a code correction to produce a pure code (PC) measurement group,        or with a phase correction to produce a mixed code (MC)        measurement group, or producing both a PC and a MC measurement        group, or    -   b. at least one measurement from the phase measurement group        with a phase correction to create a pure phase (PP) measurement        group, or with a code correction to create a mixed phase (MP)        measurement group, or producing both a PP and a MP measurement        group, or    -   c. at least one IFCP measurement with a phase correction to        produce a pure code phase (PCP) measurement group, or with a        code correction to produce a mixed code phase (MCP) measurement        group, or producing both a PCP measurement group and a MCP        measurement group, or    -   d. correct errors by error models;

g) combining at least two different measurements selected from themeasurement groups created in step (f) into code-dominated combinationsand phase-dominated measurement combinations; and

h) using one or more of a code-dominated combination in a filter whichoutputs a position and ambiguity estimate;

i) repeating steps (a)-(h) until a stable filter output is achieved; and

j) thereafter using one or more of a phase-dominated combination in thefilter.

In one embodiment, step (j) may optionally be omitted where step (h) mayutilize any measurement combination except a single frequencycombination combining a MC and a PP measurement, and steps (a) to (i)are repeated regardless of the filter status. In another embodiment,optionally steps (h) and (i) are omitted and a phase dominatedcombination is used in the filter, where step (h) may utilize anymeasurement combination except a dual frequency combination combiningpure IF phase plus pure IFCP measurement, or mixed IF code plus pure IFphase measurement.

In another aspect, the invention may comprise a device for approximatinga position using a GNSS system having a plurality of satellites and anaugmentation system, the device comprising:

-   -   (a) at least one memory, the memory containing a set of program        instructions;    -   (b) at least one processor operatively connected to the memory,        the at least one processor responsive to the program        instructions to:        -   (i) obtain an initial direct code or an initial direct phase            measurement, or both, from the GNSS satellite signals;        -   (ii) generate a code measurement group by creating at least            one code-based additional measurement;        -   (iii) generate a phase measurement group by creating at            least one phase-based additional measurement;        -   (iv) generate an IFCP measurement group by creating at least            one IFCP measurement;        -   (v) receive at least one code correction from a code based            augmentation system or at least one phase correction from a            phase based augmentation system, or both;        -   (vi) correct:            -   a. at least one measurement from the code measurement                group with a code correction or a phase correction, or                both, to produce a pure code (PC) measurement group, or                a mixed code (MC) measurement group, respectively, or            -   b. at least one measurement from the phase measurement                group with a phase correction or a code correction, or                both, to create a pure phase (PP) measurement group, or                a mixed phase (MP) measurement group, respectively, or            -   c. at least one IFCP measurement with a phase correction                or a code correction, or both, to produce a pure code                phase (PCP) measurement group, or a mixed code phase                (MCP) measurement group;        -   (vii) combine at least two different measurements selected            from the PC, MC, PP, MP, PCP and MCP groups created in            step (f) into code-dominated combinations or phase-dominated            measurement combinations, or both; and        -   (viii) use one or more of a code-dominated combination or a            phase-dominated combination, or both, in a filter which            outputs a position and ambiguity estimate; and        -   (ix) repeating steps (i)-(viii) until a stable filter output            is achieved.

In alternative embodiments, the program instructions may be toalternative embodiments of the method as described or claimed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a representative illustration of a Global Navigation SatelliteSystem (GNSS) with augmentation systems;

FIG. 2 is a schematic flowchart showing a basic method of implementingthe present invention;

FIG. 3 is a representative illustration showing the method and procedureof new measurements creation;

FIG. 4 is a representative illustration showing the method and procedureof error mitigation with the aid of augmentation corrections;

FIG. 5 is a representative illustration showing the method and procedureof generating measurement combinations.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS

The invention relates to a system and method for using code and phaseaugmentation corrections in carrier phase based GNSS positioning. Whendescribing the present invention, all terms not defined herein havetheir common art-recognized meanings. To the extent that the followingdescription is of a specific embodiment or a particular use of theinvention, it is intended to be illustrative only and not limiting ofthe claimed invention. The following description is intended to coverall alternatives, modifications and equivalents that are included in thespirit and scope of the invention, as defined in the appended claims.

FIG. 1 illustrates a representative view of Global Navigation Satellitesystem (GNSS) (100) such as GPS, GLONASS, GALILEO, Chinese COMPASS orJapanese QZSS. The GNSS (100) includes a plurality of satellites (101)transmitting signals (11) that include a data stream providinginformation regarding the satellite (101) transmitting the signal (11),through single or multiple frequency carriers. A GNSS receiver (150)receives the signals from satellites (101) and determines the positionof the receiver with measurements derived from the signals (11) from atleast four satellites (101).

The GNSS receiver (150) is provided that is operative to receive thesignals (11) transmitted by the plurality of satellites (101).Typically, the GNSS receiver must be in line of sight with a satelliteto receive the signals transmitted by that satellite. The GNSS receivercan use the signals received from the satellites 12 to determine codepseudorange and carrier phase measurements. The present invention may beimplemented with and/or incorporated into any GNSS or GPS device,including portable, handheld GPS navigation units, GPS-enabled wirelesstelephones, GPS-enabled personal digital assistants, GPS-enabled laptopcomputers, avionics equipment that incorporates GPS receivers, marineequipment that incorporates GPS receivers, and the like. Any such deviceshall be considered a GNSS receiver herein.

It is noted that the clock in a GNSS receiver is not an atomic clock,and as such does not keep the time as precisely as the satellite clocks.Therefore, each distance measurement is corrected to account for theclock error in the GNSS receiver. This distance or range correctionattributable to the clock error is termed a pseudorange. The codepseudorange measurement is the distance between one of the satellitesthat transmitted the signal and the antennas of the GNSS receiver. Bydetermining the time shift needed to align a code portion of the signalreceived from one of the satellites with a code portion of the signalgenerated by the GNSS receiver, a code pseudorange measurement can bedetermined. Using the determined time shift and the speed of light, anunambiguous approximation of the distance between the satellitetransmitting the signal and the GNSS receiver can be determined.

The carrier phase measurement uses the phase difference between acarrier portion of a received signal and an identical receiver-generatedcarrier signal to determine and even more accurately approximate thedistance between the satellite transmitting the signal and the GNSSreceiver.

The GNSS receiver can determine its position by triangulation using thetransmitted signals of a number of the satellites (typically 4 or more)to determine approximate distances between the GNSS receiver and thevarious satellites using both code pseudorange measurements and carrierphase measurements.

Along with the plurality of satellites (101) and the GNSS receiver(150), the present invention utilizes augmentation systems. Based on thecreation principle, the augmentation systems may comprise code basedaugmentation systems whose corrections are designed for correcting codemeasurements, and phase based augmentation systems whose corrections aredesigned for correcting phase measurement. Current code basedaugmentation systems include but are not limited to Satellite BasedAugmentation System (SBAS) such as the Wide Area Augmentation System(WAAS) in use in the United States, Multi functional SatelliteAugmentation System (MSAS) in Japan, European Geostationary NavigationOverlay Service (EGNOS) in Europe, GPS Aided Geo Augmented Navigation(GAGAN) in India and other SBAS systems, and local DGPS systems, CanadaCDGPS system, and India GAGAN systems. Other code based augmentationsystems may be developed and implemented. Current phase basedaugmentation system includes but are not limited to StarFire™,Omnistar™, IGS precise products, JPL real-time corrections and CORSsystems. Other phase based augmentation systems may be developed andimplemented.

Phase or code corrections may be transmitted by geostationary satellite(10(3) broadcasting a correction signal (1(3), or by Internet server(105) through Internet message (1(5), or by a ground-based line of sightradio (107) broadcasting message (17).

In the case of WAAS, a network of wide area ground reference stations(WRSs) are linked to cover a service area including the entire U.S. andsome areas of Canada and Mexico. The number of WRSs is currently aboutthirty-eight. The WRSs are precisely surveyed so that the exact locationof each WRS is known. Signals from GPS satellites are received andanalyzed by the WRSs to determine errors in the signals, includingerrors caused by the ionospheric disturbances described above. Each WRSin the network relays its data to a wide area master station (WMS) wherecorrection information is computed. The WMS calculates correctionmessages for each GPS satellite based on correction algorithms andassesses the overall integrity of the system. The correction messagesare then uplinked to a pair of Geostationary Communication Satellites(GEOs) via a ground uplink system. The GEOs broadcast the messages onthe same frequency as GPS (L1, 1575.42 MHz) to GPS receivers within thecoverage area of the WAAS satellites. The GEOs are also referred to bythose skilled in the art as SBAS or WAAS satellites.

The code corrections can include several types of error corrections,including fast corrections, slow corrections and ionosphericcorrections. The fast corrections are used to correct for rapidlychanging errors such as the fast-varying component of the clock errorsin the clocks of the satellites. The slow corrections are used tocorrect the slow-varying orbit errors as well as the slow-varyingcomponent of the clock errors in the clocks of the satellites.

The code correction is received in a message from a SBAS satellite, or aGBAS station. Data included in code correction messages includes maskdata and correction data.

One type of information that is included in the correction messages isionospheric correction data. Ionospheric corrections are broadcast forselected ionospheric grid points generally spaced at 5 degree intervalsin both latitude and longitude directions. GNSS receivers use the codecorrection to correct for GPS satellite signal errors caused byionospheric disturbances and other inaccuracies.

A system and method for applying code corrections is described inApplicant's co-pending U.S. patent application Ser. No. 12/340,119,filed on Dec. 18, 2008, the contents of which are incorporated herein,where permitted.

Once a GNSS receiver (150) receives GNSS measurements (11), newmeasurements can be created by combining different frequencymeasurements to form ionosphere free (IF) code pseudorange and IFcarrier phase measurements, combining code and phase measurements toform IF code phase measurements (IFCP) and smoothed code measurements,differencing measurements from different GNSS satellites (101) ordifferencing measurements from different measurement epochs. All theseoriginal and created measurements may be corrected by the augmentationcorrections received through a correction message (13, 15 and/or 17)before position determination. The original measurements, which have notbeen combined or differenced from any other measurements, are referredto herein as direct measurements herein.

In one embodiment, the invention comprises a method for approximating aposition using a GNSS system having a plurality of GNSS satellites andone or more augmentation systems, the method comprising: (a) obtaining adirect code or a direct phase measurement, or both, from the GNSSsatellite signals; (b) generating a code measurement group by creatingat least one code-based additional measurement; (c) generating a phasemeasurement group by creating at least one phase-based additionalmeasurement; (d) generating an IFCP measurement group by creating atleast one IFCP measurement; (e) receiving at least one code correctionfrom a code based augmentation system or at least one phase correctionfrom a phase based augmentation system, or both; (f) correcting:

-   -   a. at least one measurement from the code measurement group with        a code correction or a phase correction, or both, to produce a        pure code (PC) measurement group, or a mixed code (MC)        measurement group, respectively, or    -   b. at least one measurement from the phase measurement group        with a phase correction or a code correction, or both, to create        a pure phase (PP) measurement group, or a mixed phase (MP)        measurement group, respectively, or    -   c. at least one IFCP measurement with a phase correction or a        code correction, or both, to produce a pure code phase (PCP)        measurement group, or a mixed code phase (MCP) measurement        group;        (g) combining at least two different measurements selected from        the PC, MC, PP, MP, PCP and MCP groups created in step (f) into        code-dominated combinations and phase-dominated measurement        combinations; and (h) using a code-dominated combination in a        filter which outputs a position and ambiguity estimate; and        repeating steps (a)-(h) until a stable filter output is        achieved. Once a stable filter output is achieved, in one        embodiment, a phase-dominated measurement combination may be        used in the filter.

In one embodiment, step (j) may optionally be omitted where step (h) mayutilize any measurement combination except a single frequencycombination combining a MC and a PP measurement, and steps (a) to (i)are repeated regardless of the filter status. In another embodiment,optionally steps (h) and (i) are omitted and a phase dominatedcombination is used in the filter, where step (h) may utilize anymeasurement combination except a dual frequency combination combiningpure IF phase plus pure IFCP measurement, or mixed IF code plus pure IFphase measurement.

As used herein, a “pure measurement” is a measurement which has beencorrected by the correction developed for that particular measurementtype. A “mixed measurement” is a measurement which has been corrected bya correction not purposely designed for it.

In another embodiment, the step (h) comprising two sub steps ascode-dominated combination followed by phase-dominated combination, in afilter which outputs a position and ambiguity estimate.

In another embodiment, there could be no code and/or phase correctionsand the system will treat the absent corrections as zeros.

FIG. 2 shows a basic flowchart of one embodiment of the presentinvention. Direct GNSS measurements (11) from satellites (101) arereceived in step 201 and are then used to create additional measurementsin step 203 based on the direct measurements (11). All of the direct andcreated additional measurements are corrected with the aid of eithercode corrections or phase corrections in step 205 to create two or morecorrected measurements. These corrected measurements will then begrouped into different combinations in step 207. One combination willthen be selected for position determination based on the condition of afilter in step 209 and the position will be determined by a filteringstep (step 211). These steps may be repeated on a periodic basis inorder to update the receiver position, or to refine the accuracy of thereceiver position.

In one embodiment, the order of different steps in FIG. 2 may be varied.For example, measurement combinations (step 207) may be made ahead ofthe error mitigation step (205).

FIG. 3 illustrates schematically one embodiment of the method andstrategy of measurement creation. The direct measurements for a GNSSreceiver (150) include initial code (301) and initial phase (303)measurements. The code (301) measurement can either be directly used forpositioning, referred to as direct code (311) or be smoothed withcarrier phase measurements to form smoothed code (312). The followingequation shows an example of this smoothing process:

$\begin{matrix}{{\rho\left( t_{i} \right)}_{sm} = \frac{{\rho\left( t_{i} \right)} + {\left( {k - 1} \right) \times \left\lbrack {{\rho\left( t_{i - 1} \right)}_{sm} + \phi_{i} - \phi_{i - 1}} \right\rbrack}}{k}} & (1)\end{matrix}$where:

-   -   ρ(t_(i))_(sm) is the smoothed code pseudorange at time t_(i)    -   ρ(t_(i)) is the code pseudorange measurement at time t_(i)    -   ρ(t_(i-1))_(sm) is the smoothed code pseudorange from the prior        epoch    -   φ_(i) is the instantaneous carrier phase measurement at time        t_(i)    -   φ_(i-1) is the instantaneous carrier phase measurement from the        prior epoch; and    -   k is a weighting factor, with larger values indicating a greater        amount of smoothing        when multiple frequency measurements are available, code (301)        can be also be made as ionosphere free code measurements with        both direct and smooth code measurements to form ionosphere free        code (319) and ionosphere free smoothed code (320), for example,        by the following equation:

$\begin{matrix}{P_{{Ionosphere}\mspace{14mu}{Free}} = \frac{{f_{1}^{2}P_{1}} - {f_{2}^{2}P_{2}}}{f_{1}^{2} - f_{2}^{2}}} & (2)\end{matrix}$A phase measurement (303) can either be directly used for positioning,referred to as direct phase (351) or be made as ionosphere freecombination, referred to as ionosphere free phase (359), as long asmultiple frequency measurement is available, by the following equation:

$\begin{matrix}{\phi_{{Ionosphere}\mspace{14mu}{Free}} = \frac{{f_{1}^{2}\phi_{1}} - {f_{2}^{2}\phi_{2}}}{f_{1}^{2} - f_{2}^{2}}} & (3)\end{matrix}$An Ionosphere Free Code Phase (IFCP) measurement (333) can be generatedby combining code (301) and phase (303) as the following equation:

$\begin{matrix}{{IFCP} = \frac{P + \phi}{2}} & (4)\end{matrix}$

As shown schematically in FIG. 3, additional new code measurements canbe created as follows:

-   -   inter-satellite single differenced code (313) can be generated        by inter-satellite differencing direct code (311)    -   inter-satellite single differenced smoothed code (314) can be        generated by inter-satellite differencing smoothed code (312)    -   inter-epoch single differenced code (315) can be generated by        inter-epoch differencing direct code (311)    -   inter-epoch single differenced smoothed code (316) can be        generated by inter-epoch differencing smoothed code (312)    -   inter-satellite inter-epoch double differenced code (317) can be        generated by inter-satellite inter-epoch double differencing        direct code (311)    -   inter-satellite inter-epoch double differenced smoothed code        (318) can be generated by inter-satellite inter-epoch double        differencing smoothed code (312)    -   inter-satellite single differenced ionosphere free code (321)        can be generated by inter-epoch differencing ionosphere free        code (319)    -   inter-satellite single differenced ionosphere free smoothed code        (322) can be generated by inter-epoch differencing ionosphere        free smoothed code (320)    -   inter-epoch single differenced ionosphere free code (323) can be        generated by inter-epoch differencing ionosphere free code (319)    -   inter-epoch single differenced ionosphere free smoothed code        (324) can be generated by inter-epoch differencing ionosphere        free smoothed code (320)    -   inter-satellite, inter-epoch double differenced ionosphere free        code (325) can be generated by inter-satellite inter-epoch        double differencing ionosphere free code (319)    -   inter-satellite, inter-epoch double differenced ionosphere free        smoothed code (326) can be generated by inter-satellite        inter-epoch double differencing ionosphere free smoothed code        (320).        All such measurements generated from code measurement are        referred to herein as the code measurement group (310).

Additional new IFCP measurements can be created as follows:

-   -   inter-satellite single differenced IFCP (335) can be generated        by inter-satellite differencing IFCP (333)    -   as inter-epoch single differenced IFCP (337) be generated by        inter-epoch differencing IFCP (333)    -   inter-satellite, inter-epoch double differenced IFCP (339) can        be generated by inter-satellite inter-epoch double differencing        IFCP (333)        All such measurements generated from IFCP (333, 335, 337 and        339) are referred to herein as the IFCP measurement group (330).

Additional new phase measurements can be created as follows:

-   -   inter-satellite single differenced phase (353) can be generated        by inter-satellite differencing direct phase (351)    -   inter-epoch single differenced phase (355) can be generated by        inter-epoch differencing direct phase (351)    -   inter-satellite, inter-epoch double differenced phase (357) can        be generated by inter-satellite inter-epoch double differencing        direct phase (351)    -   inter-satellite single differenced ionosphere free phase (361)        can be generated by inter-epoch differencing ionosphere free        phase (359)    -   inter-epoch single differenced ionosphere free phase (363) can        be generated by inter-epoch differencing ionosphere free phase        (359    -   inter-satellite, inter-epoch double differenced ionosphere free        phase (365 can be generated by inter-satellite inter-epoch        double differencing ionosphere free phase (359)        All such phase measurements generated from phase measurement        (303) will be referred to as phase measurement group (350).

FIG. 4 illustrates one embodiment of an error correction strategy fordifferent measurements. Errors or corrections common to both code andphase measurements, including but not limited to troposphere delay,ionosphere delay, Sagnac effect, relativity effect, and earth tidecompensation, are not listed here, but may be implemented by thoseskilled in the art. Also, errors different for code and phase but whichcould be modeled by those skilled in the art, including but not limitedto phase windup for carrier phase measurements, are also not listedhere. The method illustrated in FIG. 4 only demonstrates errorcorrections specific to code or phase measurements. Code measurementgroup (310) is equivalent to code measurement group (411). IFCPmeasurement group (330) is equivalent to IFCP measurement group (413).Phase measurement group (350) is equivalent to phase measurement group(415).

After common and modeled corrections, code measurement group (411) canbe corrected by code specific corrections (401) from code basedaugmentation systems to generate pure code group (421), which includesmeasurements such as:

-   -   Pure Direct Code (PDC)    -   Pure inter-Satellite Single Differenced Code (PSSDC)    -   Pure inter-Epoch Single Differenced Code (PESDC)    -   Pure inter-Satellite Inter-Epoch Double Differenced Code        (PSEDDC)    -   Pure Smoothed Code (PSC)    -   Pure inter-Satellite Single Differenced Smoothed Code (PSSDSC)    -   Pure inter-Epoch Single Differenced Smoothed Code (PESDSC)    -   Pure inter-Satellite Inter-Epoch Double Differenced Smoothed        Code (PSEDDSC)    -   Pure Ionosphere free Code (PIC)    -   Pure inter-Satellite Single Differenced Ionosphere free Code        (PSSDIC)    -   Pure inter-Epoch Single Differenced Ionosphere free Code        (PESDIC)    -   Pure inter-Satellite inter-Epoch Double Differenced Ionosphere        free Code (PSEDDIC)    -   Pure Ionosphere free Smoothed Code (PISC) Pure inter-Satellite        Single Differenced Ionosphere free Smoothed Code (PSSDISC)    -   Pure inter-Epoch Single Differenced Ionosphere free Smoothed        Code (PESDISC)    -   Pure inter-Satellite inter-Epoch Double Differenced Ionosphere        free Smoothed Code (PSEDDISC)        The pure code measurement group is designated as “PC” and any        measurement in this group is designated “P*C”, where the        asterisk indicates letter(s) which determine the specific pure        code measurement.

Code measurement group (411) can also be corrected by phase specificcorrections (403) from phase based augmentation systems to generate amixed code measurement group (422), which includes measurements such as:

-   -   Mixed Direct Code (MDC)    -   Mixed inter-Satellite Single Differenced Code (MSSDC)    -   Mixed inter-Epoch Single Differenced Code (MESDC)    -   Mixed inter-Satellite inter-Epoch Double Differenced Code        (MSEDDC)    -   Mixed Smoothed Code (MSC)    -   Mixed inter-Satellite Single Differenced Smoothed Code (MSSDSC)    -   Mixed inter-Epoch Single Differenced Smoothed Code (MESDSC)    -   Mixed inter-Satellite inter-Epoch Double Differenced Smoothed        Code (MSEDDSC)    -   Mixed Ionosphere free Code (MIC)    -   Mixed inter-Satellite Single Differenced Ionosphere free Code        (MSSDIC)    -   Mixed inter-Epoch Single Differenced Ionosphere free Code        (MESDIC)    -   Mixed inter-Satellite inter-Epoch Double Differenced Ionosphere        free Code (MSEDDIC)    -   Mixed Ionosphere free Smoothed Code (MISC)    -   Mixed inter-Satellite Single Differenced Ionosphere free        Smoothed Code (MSSDISC)    -   Mixed inter-Epoch Single Differenced Ionosphere free Smoothed        Code (MESDISC)    -   Mixed inter-Satellite inter-Epoch Double Differenced Ionosphere        free Smoothed Code (MSEDDISC)        The mixed code measurement group (422) is designated as “MC” and        any measurement in this group is designated as “M*C”, where the        asterisk indicates letter(s) which determine the specific mixed        code measurement.

After common and modeled corrections, IFCP measurement group (413) canbe corrected by phase specific corrections (403) from phase basedaugmentation systems to generate a pure code phase measurement group(423), which includes measurements such as:

-   -   Pure Code Phase (PCP)    -   Pure inter-Satellite Single Differenced Code Phase (PSSDCP)    -   Pure inter-Epoch Single Differenced Code Phase (PESDCP)    -   Pure inter-Satellite inter-Epoch Double Differenced Code Phase        (PSEDDCP)        The pure code phase measurement group (423) is designated as        “PCP” and any measurement in this group is designated as “P*CP”,        where the asterisk indicates letter(s) which determine the        specific pure code phase measurement.

IFCP measurement group (413) can also be corrected by code specificcorrections 401 from code based augmentation systems to generate a mixedcode phase measurement group (425), which includes measurements such as:

Mixed Code Phase (MCP)

-   -   Mixed inter-Satellite Single Differenced Code Phase (MSSDCP)    -   Mixed inter-Epoch Single Differenced Code Phase (MESDCP)    -   Mixed inter-Satellite inter-Epoch Double Differenced Code Phase        (MSEDDCP)        The mixed code phase measurement group (425) is designated as        “MCP” and any measurement in the group is designated as “M*CP”,        where the asterisk indicates letter(s) which determine the        specific mixed code phase measurement.

After common and modeled corrections, phase measurement group (415) canbe corrected by phase specific corrections (403) from phase basedaugmentation systems to generate a pure phase measurement group (427),which includes measurements such as:

Pure Direct Phase (PDP)

-   -   Pure inter-Satellite Single Differenced Phase (PSSDP)    -   Pure inter-Epoch Single Differenced Phase (PESDP)    -   Pure inter-Satellite inter-Epoch Double Differenced Phase        (PSEDDP)    -   Pure Ionosphere free Phase (PIP)    -   Pure inter-Satellite Single Differenced Ionosphere free Phase        (PSSDIP)    -   Pure inter-Epoch Single Differenced Ionosphere free Phase        (PESDIP)    -   Pure inter-Satellite inter-Epoch Double Differenced Ionosphere        free Phase (PSEDDIP)        The pure phase measurement group (427) is designated as “PP” and        any measurement in this group is designated as “P*P”, where the        asterisk indicates letter(s) which determine the specific pure        phase measurement.

Phase measurement group (415) can also be corrected by code specificcorrections (401) from code based augmentation systems to generate amixed phase measurement group (429), which includes measurements suchas:

-   -   Mixed Direct Phase (MDP)    -   Mixed inter-Satellite Single Differenced Phase (MSSDP)    -   Mixed inter-Epoch Single Differenced Phase (MESDP)    -   Mixed inter-Satellite inter-Epoch Double Differenced Phase        (MSEDDP)    -   Mixed Ionosphere free Phase (MIP)    -   Mixed inter-Satellite Single Differenced Ionosphere free Phase        (MSSDIP)    -   Mixed inter-Epoch Single Differenced Ionosphere free Phase        (MESDIP)    -   Mixed inter-Satellite inter-Epoch Double Differenced Ionosphere        free Phase (MSEDDIP)        The mixed phase measurement group (429) is designated as “MP”        and any measurement in this group is designated as “M*P”, where        the asterisk indicates letter(s) which determine the specific        mixed phase measurement.

FIG. 5 illustrates one embodiment of a procedure for creating ameasurement combination. The measurement groups shown in FIG. 5 areequivalent to those shown in FIG. 4. (pure code group 421 is equivalentto 501; pure code phase group 423 is equivalent to 503; pure phase group427 is equivalent to 507; mixed code group 422 is equivalent to 502;mixed code phase group 425 is equivalent to 505; mixed phase group 429is equivalent to 509. The selection of measurements from the differentmeasurement groups determines whether the measurement combination iscode-dominated or phase-dominated and whether the measurementcombination is pure or mixed.

A code-dominated pure combination (521) is formed when one measurementfrom pure code group (501) plus at least one measurement from pure codephase group (503) and pure phase group (507) are combined together toform one of a number of possible code-dominated pure combinations. Table1 provides exemplary possible code-dominated pure combinations withsingle frequency systems:

TABLE 1 Direct code-dominated pure PDC plus one or more of PDP and PCPSmoothed code-dominated pure PSC plus one or more of PDP, PDC and PCPInter-Satellite single differenced PSSDC plus one or more of PSSDPcode-dominated pure and PSSDCP Inter-Satellite single differenced PSSDSCplus one or more of PSSDP, smoothed code-dominated pure PSSDC and PSSDCPInter-Epoch single differenced PESDC plus one or more of PESDPcode-dominated pure and PESDCP Inter-Epoch single differenced PESDSCplus one or more of PESDP, smoothed code-dominated pure PESDC and PESDCPInter-satellite inter-epoch double PSEDDC plus one or more of PSEDDPdifferenced code-dominated pure and PSEDDCP Inter-satellite inter-epochdouble PSEDDSC plus one or more of differenced smoothed code- PSEDDP,PSEDDC and PSEDDCP dominated pure

For multiple frequency systems, the code-dominated pure combination(521) includes those of the single frequency measurements and also themeasurements shown in Table 2.

TABLE 2 Direct code-dominated pure PDC plus PIP PDC plus PIP plus one ormore of PIC, PISC, PCP and PDP Smoothed code-dominated PSC plus PIP purePSC plus PIP plus one or more of PIC, PISC, PCP, PDC and PDPInter-Satellite single PSSDC plus PSSDIP differenced code-dominatedPSSDC plus PSSDIP plus one or more of pure PSSDIC, PSSDISC, PSSDDP andPSSDCP Inter-Satellite single PSSDSC plus PSSDIP differenced smoothedcode- PSSDSC plus PSSDIP plus one or more dominated pure of PSSDIC,PSSDISC, PSSDDP, PSSDC and PSSDCP Inter-Epoch single differenced PESDCplus PESDIP code-dominated pure PESDC plus PESDIP plus one or more ofPESDIC, PESDISC, PESDDP and PESDCP Inter-Epoch single differenced PESDSCplus PESDIP smoothed code-dominated PESDSC plus PESDIP plus one or morepure of PESDIC, PESDISC, PESDDP, PESDC and PESDCP Inter-satelliteinter-epoch PSEDDC plus PSEDDIP double differenced code- PSEDDC plusPSEDDIP plus one or dominated pure more of PSEDDIC, PSEDDISC, PDDDP andPSEDDCP Inter-satellite inter-epoch PSEDDSC plus PSEDDIP doubledifferenced smoothed PSEDDSC plus PSEDDIP plus one or code-dominatedpure more of PSEDDIC, PSEDDISC, PDDDP, PESDSC and PSEDDCP

Code-dominated mixed measurement combinations (523) are formed when onemeasurement from pure code group (501) or mixed code group (502) plus atleast one measurement from pure code phase group (503), pure phase group(507), mixed code phase (505) and mixed phase group (509) are combinedtogether, and at least one of the measurements used is mixed. Table 3provides possible code-dominated mixed combinations with singlefrequency measurements:

TABLE 3 Direct code-dominated MDC/PDC plus one or more of PCP, PDP,mixed MCP and MDP with at least one mixed measurement used Smoothcode-dominated MSC/PSC plus one or more of PCP, PDP, mixed MCP, MDC, PDCand MDP with at least one mixed measurement used Inter-Satellite singleMSSDC/PSSDC plus one or more of differenced code-dominated PSSDP,PSSDCP, MSSDP and MSSDCP mixed with at least one mixed measurement usedInter-Satellite single MSSDSC/PSSDSC plus one or more of differencedsmoothed code- PSSDP, PSSDCP, MSSDP, MSSDC, dominated mixed PSSDC andMSSDCP with at least one mixed measurement used Inter-Epoch singleMESDC/PESDC plus one or more of differenced code-dominated PESDP,PESDCP, MESDP and MESDCP mixed with at least one mixed measurement usedInter-Epoch single MESDSC/PESDSC plus one or more of differencedsmoothed code- PESDP, PESDCP, MESDP, MESDC, dominated mixed PESDC andMESDCP with at least one mixed measurement used Inter-satelliteinter-epoch MSEDDC/PSEDDC plus one or more of double differenced code-PSEDDP, PSEDDCP, MSEDDP and dominated pure MSEDDCP with at least onemixed measurement used Inter-satellite inter-epoch MSEDDSC/PSEDDSC plusone or more of double differenced PSEDDP, PSEDDCP, MSEDDP, MSEDDC,smoothed code-dominated PSEDDC and MSEDDCP with at least one pure mixedmeasurement used

For multiple frequency systems, code-dominated mixed measurementcombination (523) includes those of the single frequency measurementsand also the measurements shown in Table 4.

TABLE 4 Direct code- MDC/PDC plus MIP/PIP dominated mixed MDC/PDC plusMIP/PIP plus one or more of PIC, PCP, PDP, MIC, MCP and MDP With atleast one mixed measurement used Smoothed code- MSC/PSC plus MIP/PIPdominated MSC/PSC plus MIP/PIP plus one or more of PIC, mixed PISC, PCP,PDP, MIC, MISC, MCP, MDC, PDC and MDP With at least one mixedmeasurement used Inter-Satellite single MSSDC/PSSDC plus MSSDIP/PSSDIPdifferenced code- MSSDC/PSSDC plus MSSDIP/PSSDIP plus one or dominatedpure more of PSSDIC, PSSDDP, PSSDCP, MSSDIC, MSSDDP and MSSDCP With atleast one mixed measurement used Inter-Satellite single MSSDSC/PSSDSCplus MSSDIP/PSSDIP differenced MSSDSC/MSSDSC plus MSSDIP/PSSDIP plussmoothed one or more of PSSDIC, PSSDISC, PSSDDP, code-dominated PSSDCP,MSSDIC, MSSDISC, MSSDDP, pure MSSDC, PSSDC and MSSDCP With at least onemixed measurement used Inter-Epoch single MESDC/PESDC plus MESDIP/PESDIPdifferenced code- MESDC/PESDC plus MESDI/PESDIP plus one or dominatedpure more of PESDIC, PESDDP, PESDCP, MESDIC, MESDDP and MESDCP With atleast one mixed measurement used Inter-Epoch single MESDSC/PESDSC plusMESDIP/PESDIP differenced MESDSC/PESDSC plus MESDIP/PESDIP plus onesmoothed or more of PESDIC, PESDISC, PESDDP, PESDCP, code-dominatedMESDIC, MESDISC, MESDDP, MESDC, PESDC pure and MESDCP With at least onemixed measurement used Inter-satellite inter- MSEDDC/PSEDDC plusMSEDDIP/PSEDDIP epoch double MSEDDC/PSEDDC plus MSEDDIP/PSEDDIP plusdifferenced code- one or more of PSEDDIC, PSEDDP, PSEDDCP, dominatedpure MSEDDIC, MSEDDP and MSEDDCP With at least one mixed measurementused Inter-satellite inter- MSEDDSC/PSEDDSC plus MSEDDIP/PSEDDIP epochdouble MSEDDSC/PSEDDSC plus MSEDDIP/PSEDDIP differenced plus one or moreof PSEDDIC, PSEDDISC, smoothed code- PSEDDP, PSEDDCP, MSEDDIC, MSEDDISC,dominated pure MSEDDP, MSEDDC, PSEDDC and MSEDDCP With at least onemixed measurement used

One or more measurements from pure code phase group (503) and pure phasegroup (507) and ionosphere free code measurements from pure code group(501 are used to develop the phase-dominated pure combination (525).Table 5 provides possible phase-dominated pure combinations with singlefrequency measurements:

TABLE 5 Direct phase-dominated pure One or more of PDP and PCPInter-satellite single differenced phase- One or more of PSSDP anddominated pure PSSDCP Inter-epoch single differenced phase- One or moreof PESDP and dominated pure PESDCP Inter-satellite inter-epoch doubleOne or more of PSEDDP and differenced phase-dominated pure PDDCP

For multiple frequency systems, a phase-dominated pure combination (525)includes those of the single frequency measurements and also themeasurements shown in Table 6.

TABLE 6 Direct phase-dominated pure PIP PIP plus one or more of PIC,PISC, PCP and PDP Inter-satellite single differenced PSSDIPphase-dominated pure PSSDIP plus one or more of PSSDIC, PSSDISC, PSSDCP,PSSDDP Inter-epoch single differenced PESDIP phase-dominated pure PESDIPplus one or more of PESDIC, PESDISC, PESDCP and PESDDP Inter-satelliteinter-epoch double PSEDDIP differenced phase-dominated PSEDDIP plus oneor more of pure PSEDDIC, PSEDDISC, PSEDDCP, PSEDDP

One or more of pure code phase group (503), mixed code phase group(505), pure phase group (507), mixed phase group (509) and ionospherefree code measurements from pure code group (501 or mixed code group(502) are used to develop phase-dominated mixed combination (527). Table7 provides possible phase-dominated mixed combinations with singlefrequency measurements.

TABLE 7 Direct phase- One or more of MDP/PDP and MCP and PCP dominatedmixed with at least one mixed measurement used Inter-satellite singleOne or more of MSSDP, PSSDP, MSSDCP and differenced phase- PSSDCP withat least one mixed measurement dominated mixed used Inter-epoch singleOne or more of MESDP/PESDP and MESDCP differenced phase- and PESDCP withat least one mixed dominated mixed measurement used Inter-satelliteinter- One or more of MSEDDP/PSEDDP and epoch double MSEDDCP and PSEDDCPwith at least one differenced phase- mixed measurement used dominatedmixed

For multiple frequency systems, phase-dominated mixed combination (527)includes those of the single frequency measurements and also themeasurements shown in Table 8.

TABLE 8 Direct phase- MIP dominated mixed MIP/PIP plus one or more ofPCP, PIC, PISC, PDP, MIC, MISC and MDP With at least one mixedmeasurement used Inter-satellite single MSSDIP differenced phase-MSSDIP/PSSDIP plus one or more of PSSDCP, dominated mixed PSSDIC,PSSDISC, PSSDP, MSSDCP, MSSDIC, MSSDISC, MSSDP With at least one mixedmeasurement used Inter-epoch single MESDIP differenced phase-MESDIP/PESDIP plus one or more of PESDCP, dominated mixed PESDIC,PESDISC, PESDP, MESDCP, MESDIC, MESDISC, MESDP With at least one mixedmeasurement used Inter-satellite inter- MSEDDIP epoch doubleMSEDDIP/PSEDDIP plus one or more of differenced phase- PESDCP, PESDIC,PESDISC, PESDP, dominated mixed MESDCP, MESDIC, MESDISC, MESDP With atleast one mixed measurement used

The present invention may also be described in the context ofcomputer-executable instructions, such as program modules, beingexecuted by a computer. Generally, program modules include routines,programs, objects, components, data structures, etc. that performparticular tasks or implement particular abstract data types.

The present invention can be realized in hardware, software, or acombination of hardware and software. The present invention can berealized in a centralized fashion in one data processing system such asa computer system, or in a distributed fashion where different elementsare spread across several interconnected data processing systems. Atypical combination of hardware and software could be a general purposecomputer system or other data processing system with a computer programthat, when being loaded and executed, controls the computer system suchthat it carries out the methods described herein.

Program instructions includes any expression, in any language, code ornotation, of a set of instructions intended to cause a data processingsystem having an information processing capability to perform aparticular function either directly or after conversion to anotherlanguage, code or notation, and/or reproduction in a different materialform.

The invention also includes an article of manufacture which comprises acomputer readable memory having computer readable statements andinstructions contained thereon for implementing one or more of themethods described above, using a data processing system.

The previous description of the disclosed embodiments is provided toenable any person skilled in the art to make or use the presentinvention. Various modifications to those embodiments will be readilyapparent to those skilled in the art, and the generic principles definedherein may be applied to other embodiments without departing from thespirit or scope of the invention. Thus, the present invention is notintended to be limited to the embodiments shown herein, but is to beaccorded the full scope consistent with the claims, wherein reference toan element in the singular, such as by use of the article “a” or “an” isnot intended to mean “one and only one” unless specifically so stated,but rather “one or more”. All structural and functional equivalents tothe elements of the various embodiments described throughout thedisclosure that are known or later come to be known to those of ordinaryskill in the art are intended to be encompassed by the elements of theclaims. Moreover, nothing disclosed herein is intended to be dedicatedto the public regardless of whether such disclosure is explicitlyrecited in the claims.

What is claimed is:
 1. A method for determining a position using a GNSSsystems having a plurality of GNSS satellites and one or moreaugmentation systems, the method comprising the step of receivingsignals transmitted by the GNSS satellites, and further comprising thesequential or non-sequential steps of: a) obtaining a direct code or adirect phase measurement, or both, from the GNSS satellite signals; b)generating a code measurement group by creating at least one code-basedadditional measurement; c) generating a phase measurement group bycreating at least one phase-based additional measurement; d) generatingan IFCP measurement group by creating at least one IFCP measurement; e)receiving at least one phase correction from a phase based augmentationsystem, and optionally, at least one code correction from a code basedaugmentation system; f) correcting one or more: a. at least onemeasurement from the code measurement group with a code correction toproduce a pure code (PC) measurement group, or with a phase correctionto produce a mixed code (MC) measurement group, or producing both a PCand a MC measurement group, or b. at least one measurement from thephase measurement group with a phase correction to create a pure phase(PP) measurement group, or with a code correction to create a mixedphase (MP) measurement group, or producing both a PP and a MPmeasurement group, or c. at least one IFCP measurement with a phasecorrection to produce a pure code phase (PCP) measurement group, or witha code correction to produce a mixed code phase (MCP) measurement group,or producing both a PCP measurement group and a MCP measurement group,or d. correct errors by error models; g) combining at least twodifferent measurements selected from the measurement groups created instep (f) into code-dominated combinations and phase-dominatedmeasurement combinations; and h) using one or more of a code-dominatedcombination in a filter which outputs a position and ambiguity estimate;i) repeating steps (a)-(h) until a stable filter output is achieved; andj) thereafter using one or more of a phase-dominated combination in thefilter; wherein the code-dominated combinations comprise acode-dominated mixed combination, and optionally, a code-dominated purecombination; and wherein the code-dominated mixed combination comprisesa measurement selected from the PC or MC measurement groups and at leastone measurement from any of MP, PP, MCP or PCP groups, provided at leastone measurement in the combination is selected from MC, MP, or MCPgroups.
 2. The method of claim 1 wherein step (j) is not reached, andsteps (a) to (i) are repeated regardless of the filter status, exceptfor using the single frequency combinations including mix direct codeplus pure direct phase.
 3. The method of claim 1 wherein steps (h) and(i) are skipped, and the method goes directly to step (j) from step (g),except for using dual frequency combinations including pure IF phaseplus pure IFCP, and mixed IF code plus pure IF phase.
 4. The method ofclaim 1 wherein the order of steps (b) to (f) may be varied, providedalways that step (e) precedes step (f).
 5. The method of claim 1 whereinthe code-dominated pure combination comprises a measurement from the PCgroup and at least one other measurement selected from the PC, PP, orPCP groups.
 6. The method of claim 5 wherein the code-dominated purecombination comprises a measurement combination of Table 1 for asingle-frequency system, or Table 1 or 2 for a multiple frequencysystem.
 7. The method of claim 1 wherein the code-dominated mixedcombination comprises a measurement combination of Table 3 for asingle-frequency system, or Table 3 or 4 for a multiple frequencysystem.
 8. The method of claim 1 wherein the GNSS system comprises GPS,GLONASS, GALILEO, Beidou, or QZSS.
 9. The method of claim 1 wherein theaugmentation system is a satellite based augmentation system, groundbased augmentation system, internet based augmentation system, or otheraugmentation systems providing code corrections only, phase correctionsonly, or both code and phase corrections.
 10. The method of claim 1wherein the code based augmentation system comprises the US Wide AreaAugmentation System, the Japanese Multi functional SatelliteAugmentation system, the European Geostationary Navigation OverlayService, Canada CDGPS system, India GAGAN system, or local DGPS systemsproviding code corrections and the phase based augmentation systemcomprises StarFire system, OmniStar system, JPL system, or CORS systemsproviding phase corrections.
 11. The method of claim 1 wherein noaugmentation corrections are applied and are treated as zeros.
 12. Amethod for determining a position using a GNSS systems having aplurality of GNSS satellites and one or more augmentation systems, themethod comprising the step of receiving signals transmitted by the GNSSsatellites, and further comprising the sequential or non-sequentialsteps of: a) obtaining a direct code or a direct phase measurement, orboth, from the GNSS satellite signals; b) generating a code measurementgroup by creating at least one code-based additional measurement; c)generating a phase measurement group by creating at least onephase-based additional measurement; d) generating an IFCP measurementgroup by creating at least one IFCP measurement; e) receiving at leastone phase correction from a phase based augmentation system, andoptionally, one code correction from a code based augmentation system;f) correcting one or more: a. at least one measurement from the codemeasurement group with a code correction to produce a pure code (PC)measurement group, or with a phase correction to produce a mixed code(MC) measurement group, or producing both a PC and a MC measurementgroup, or b. at least one measurement from the phase measurement groupwith a phase correction to create a pure phase (PP) measurement group,or with a code correction to create a mixed phase (MP) measurementgroup, or producing both a PP and a MP measurement group, or c. at leastone IFCP measurement with a phase correction to produce a pure codephase (PCP) measurement group, or with a code correction to produce amixed code phase (MCP) measurement group, or producing both a PCPmeasurement group and a MCP measurement group, or d. correct errors byerror models; g) combining at least two different measurements selectedfrom the measurement groups created in step (f) into code-dominatedcombinations and phase-dominated measurement combinations; and h) usingone or more of a code-dominated combination in a filter which outputs aposition and ambiguity estimate; i) repeating steps (a)-(h) until astable filter output is achieved; and j) thereafter using one or more ofa phase-dominated combination in the filter; wherein the phase-dominatedcombinations comprise a phase-dominated pure combination, and,optionally, a phase-dominated mixed combination; and wherein thephase-dominated pure combination comprises a measurement from the PPgroup and at least one other measurement selected from the PP, PC or PCPgroups.
 13. The method of claim 12 wherein steps (h) and (i) areskipped, and the method goes directly to step (j) from step (g), exceptfor using dual frequency combinations including pure IF phase plus pureIFCP, and mixed IF code plus pure IF phase.
 14. The method of claim 12wherein the order of steps (b) to (f) may be varied, provided alwaysthat step (e) precedes step (f).
 15. The method of claim 12 wherein thephase-dominated mixed combination comprises a measurement selected fromthe PP or MP measurement groups and at least one measurement from any ofMC, PCP or MCP groups, provided that at least one measurement in thecombination is selected from MC, MP or MCP groups.
 16. The method ofclaim 12 wherein the phase-dominated pure combination comprises ameasurement combination of Table 5 for a single-frequency system orTable 5 or 6 for a multiple frequency system.
 17. The method of claim 12wherein the phase-dominated mixed measurement comprises a measurementcombination of Table 7 for a single-frequency system, or Table 7 or 8for a multiple frequency system.
 18. The method of claim 12 wherein theGNSS system comprises GPS, GLONASS, GALILEO, Beidou, or QZSS.
 19. Themethod of claim 12 wherein the augmentation system is a satellite basedaugmentation system, ground based augmentation system, internet basedaugmentation system or other augmentation systems providing codecorrections only, phase corrections only, or both code and phasecorrections.
 20. The method of claim 12 wherein the code basedaugmentation system comprises the US Wide Area Augmentation System, theJapanese Multi functional Satellite Augmentation system, the EuropeanGeostationary Navigation Overlay Service, Canada CDGPS system, IndiaGAGAN system, or local DGPS systems providing code corrections and thephase based augmentation system comprises StarFire system, OmniStarsystem, JPL system, or CORS systems providing phase corrections.
 21. Themethod of claim 12 wherein no augmentation corrections are applied andare treated as zeros.
 22. A method for determining a position using aGNSS systems having a plurality of GNSS satellites and one or moreaugmentation systems, the method comprising the step of receivingsignals transmitted by the GNSS satellites, and further comprising thesequential or non-sequential steps of: a) obtaining a direct code or adirect phase measurement, or both, from the GNSS satellite signals; b)generating a code measurement group by creating at least one code-basedadditional measurement; c) generating a phase measurement group bycreating at least one phase-based additional measurement; d) generatingan IFCP measurement group by creating at least one IFCP measurement; e)receiving at least one code correction from a code based augmentationsystem; f) correcting one or more: a. at least one measurement from thecode measurement group with a code correction to produce a pure code(PC) measurement group, or b. at least one measurement from the phasemeasurement group with a code correction to create a mixed phase (MP)measurement group, or c. at least one IFCP measurement with a codecorrection to produce a mixed code phase (MCP) measurement group, or d.correct errors by error models; g) combining at least two differentmeasurements selected from the measurement groups created in step (f)into code-dominated combinations and phase-dominated measurementcombinations; and h) using one or more of a code-dominated combinationin a filter which outputs a position and ambiguity estimate; i)repeating steps (a)-(h) until a stable filter output is achieved; and j)thereafter using one or more of a phase-dominated combination in thefilter; wherein the code-dominated combinations comprise acode-dominated mixed combination comprising at least one differencedcombination.
 23. The method of claim 22 wherein step (j) is not reached,and steps (a) to (i) are repeated regardless of the filter status. 24.The method of claim 22 wherein steps (h) and (i) are skipped, and themethod goes directly to step (j) from step (g).
 25. The method of claim22 wherein the order of steps (b) to (f) may be varied, provided alwaysthat step (e) precedes step (f).
 26. The method of claim 22 wherein thecode-dominated pure combination comprises a measurement combination ofTable 1 for a single-frequency system, or Table 1 or 2 for a multiplefrequency system.
 27. The method of claim 22 wherein the phase-dominatedmixed measurement comprises a measurement combination of Table 7 for asingle-frequency system, or Table 7 or 8 for a multiple frequencysystem.
 28. The method of claim 22 wherein the GNSS system comprisesGPS, GLONASS, GALILEO, Beidou, or QZSS.
 29. The method of claim 22wherein the augmentation system is a satellite based augmentationsystem, ground based augmentation system, internet based augmentationsystem or other augmentation systems providing code corrections only,phase corrections only, or both code and phase corrections.
 30. Themethod of claim 22 wherein the code based augmentation system comprisesthe US Wide Area Augmentation System, the Japanese Multi functionalSatellite Augmentation system, the European Geostationary NavigationOverlay Service, Canada CDGPS system, India GAGAN system, or local DGPSsystems providing code corrections and the phase based augmentationsystem comprises StarFire system, OmniStar system, JPL system, or CORSsystems providing phase corrections.
 31. The method of claim 22 whereinno augmentation corrections are applied and are treated as zeros.